The BEA air accident investigation agency blames a combination of "human and technical factors" and has recommended better training for pilots and stricter plane certification rules.

Today's report, the result of a three year probe, includes information from the jet's two black box flight recorders, recovered from the ocean in a costly and extraordinarily complex search involving robotic submarines.

One of the flight recorders Credit: REUTERS/Charles Platiau

One of the fatal decisions highlighted by the report is that the two pilots nosed the Airbus A330 upward during a stall - instead of downward, as they should have.

Chief investigator Alain Bouillard said they never understood that the plane was in a stall, partly because of false data from sensors about the plane's position. "In this case, the crew was in a state of near-total loss of control," he said.

The two co-pilots failed to carry out a basic manoeuvre for stall recovery which pilots are taught at the outset of their flight training.

Much attention has focussed on the role of pitot tubes - devices on the outside of the place which measure speed and help the pilots to understand the positioning of the jet.

During the flight, the tubes became blocked by ice crystals as the plane flew through a storm, and started providing incorrect information. Mr Bouillard said that the failure of the pitot tubes was the "unleashing event" that led to the crash.

Airbus, manufacturer of the A330 plane, said in a statement that it is working to improve pitot tubes and making other efforts to avoid future such accidents.

Fragments of the jet recovered from the ocean Credit: APTN

William Voss, president of the Flight Safety Foundation in Virginia in the US, has said that the accident was caused by the pilots' over-reliance on automation.

He claims that after they were forced to fly manually when the automation failed, they were unable to look through the conflicting information and understand what the aircraft was actually doing.

Pilots a generation ago would have done that and understood what was going on, but [the pilots] were so conditioned to rely on the automation that they were unable to do this. This is a problem not just limited to Air France or Airbus. It's a problem we're seeing around the world because pilots are being conditioned to treat automated processed data as truth, and not compare it with the raw information that lies underneath.